Fuel pump



Feb. 23, 1943. s. A. WAHLMARK 2,311,916

rum. mr

"Filed June 24. '1939 Application June 24, 1939, Serial No. 281,027

2 Claims.

pumps of the type used with domestic-cil burners, and to a means for preventing hum during operation oi the pumping mechanism.

In an oil burner installation, an objectionable hum is sometimes encountered. Many attempts have been made to eliminate this noise, but invariably the means provided functions in such a manner that the noise recurs as the fuel tank empties or after the oil burner has been started a number of times. Itis the general object of this invention to provide a new and improved fuel pump having means for eliminating such noise.

A further object is to provide a fuel pump having a casing provided with a removable closure and en anti-hum device associated therewith.

Another .object is to provide a fuel pump with a closed air chamber associated with the fuel on the intake side of the pumping mechanism, said air chamber being provided with one wall formed of an impregnated cloth, generally referred to as airplane" cloth, this cloth diaphragm serving to seal a quantity of air within said chamber.

Another object is to provide a fuel pump with means associated with the intake and with a bypassreturn passage for eliminating hum.

(Cl. S-223) More particularly, the invention relates to fuel A shaft, and a strainer 2t. A control valve mechanism forms no part of the present invention but together with other parts of the pump is claimed in said prior application. It is contemplated that the shaft 22 will be connected by suitable means to a driving motor (not shown), and that an inlet port 26 will be connected to a source of fuel supply such as a. tank (not shown). The casing parts is and 2li are formed to provide a somewhat cylindrical chamber or recess 28 in which the pumping mechanism 2l and strainer 2t are positioned` Other objects will become readily apparent from the following detailed description taken in connection with the accompanying drawing, in which:

Fig. i is a longitudinal, vertical section through a preferred form of the invention.

Fig. 2 is a fragmentary view approximately along the line 2--2 of Fig. l.

Fig. 3 is a fragmentary section in the same plane as Fig. 1 through a modified form of the invention.

Fig. 4 is a similar fragmentary view through still another form of the invention.

While I have illustrated in the drawing and shall hereafter describe in detail a preferred form of the invention, together with modifications thereof, it is to be understood that I do not intend to limit the invention to the particular forms and arrangements shown. The scope of the invention will be defined by the appended claims.

In the form selected for purposes of disclosure, the inventionis embodied in a fuel pump of the type disclosed and claimed in Patent No. 2,232,983, dated February 25, 1941, which issued on applicants copending application, Serial No. 212.475, filed June 8, 1938. As shown in Figs. 1 and 2, the fuel pump consists generally of s two-part casing l, 2e, a pumping device or mechanism 2 l,

l drive shaft 22. a mechanical seal 23, for th drive The pumping mechanism generally consists of an externally toothed roller 3G secured to the shaft 22 by a pin 3i, an internally toothed ring 32 having the lower portion thereof meshing with the roller 35 and an intermediate crescent guard 33. The complete details of this mechanism are disclosed in said copending application and function in a well .known manner to draw fuel in through the inlet port 25, through the chamber 28 and in through an intake port et formed in an end plate 35 of the pumping mechanism. Upon rotation of the shaft 22 in a clockwise direction, as

shown in Fig. 2, the fuel is carried in the cavities of the roller and ring past the crescent guide E3 and forced out through a discharge port 36. The

strainer 2d -is cup-shaped and surrounds the pumping mechanism so that all of the fuel entering the inlet port 26 must pass through the strainer to reach the intake port Si.

The fuel discharged through the port Se is conducted to the valve mechanism 25 as shown more fully in said copending application, and from said valve mechanism passes either through an outlet port adapted for connection to the oil burner or through a bypass port l (Fig. i).

At its upper end, the bypass port 2 extends up to the chamber 2e so that the bypassed oil :iows through this chamber. A plug 27' is inserted in the lower end 21" of the bypass port 2i.

In order to eliminate the hum which some-.

times occurs during operation of the pumping mechanism, a closed air pocket is formed in a portion of the chamber 28. As illustrated in Fis. 1, such an air pocket 38 is formed in the casing part 29 by stretching a diaphragm across the end of the chamber 25 and securing it in position by clamping it between the adjacent surfaces of the parts I8 and 20, these parts being secured tou gether by means of a plurality of headed screw devices l0. The diaphragm 39 is preferably made of a fuel resistant material, such as an impregnated cloth generally referred to as airplane" cloth. The left-hand or inner surface of this diaphragm forms one wall of the air pocket te,

s' the riihuhand or outer surface o the lragm forms an end wall of the chamber 2S, so as to be subjected to the fuel in said chamber.

The objectionable hum which occurs during the operation of a fuel pump is generally caused by the pulsations on the intake side of the pump. These pulsations are eliminated by the cushioning effect of the yleldable diaphragm which forms one Wall of the closed air pocket.

In the form illustrated in Fig. 3, the casing part 20 has a recess 45 in its inner surface forming an air pocket or chamber. A diaphragm 3a closes the recess 65 and is secured in place on the casing part 20' by means of a suitable ring ri. In this form. the pumping mechanism 2l is located in a chamber 28 and a strainer 24' is positioned intermediate the inlet port 26 and the pumping mechanism. Here again, a closed air pocket is formed Within the casing and has one wall thereof formed by a diaphragm of airplane cloth which is subjected to the fuel within the chamber 28.

In the form illustrated in Fig. 4, the casing part I9 and the pumping mechanism are in the same form as shown in Figs. 1 to 3. A strainer 2d surrounding the pumping mechanism is doubled-back at the left-hand end to provide a space for an anti-hum device designated generally 50. This device consists of a ring El having diaphragme 52 and 53 stretched across the opposite ends thereof and clamped thereagainst by means oi clamping rings E@ and 55 which are suitably secured to the ring iii. This anti-hum device may be supported on the strainer as shown in Fig. i instead of being fastened to the casing part but preferably the ring ft is secured in air tight relation to the adjacent surface of the casing es by means of solder or suitable screw ldevices (not shown). Connecting ports-ii? and in the casing part communicate with a port 5G in the'c'asing part I9 which in turn connects with. the bypass port 2l of the unit.

The invention provides a simple and inexpensive means for preventing hum during operation oi the 'uel unit. In the forms illustrated in Figs l to A3, wherein the internal bypass is in use, the bypassed oil, as well as the incoming oil. passes through the chamber 2B, one wall of which is loi-med by the diaphragm 39 of the closed air pocket. When the fuel unit is used in a circuit having' a reti .ut to 'the tenir. the iorm illustrated in .i g. may be used. The return conduit is connected to the lower end 2l of the bypass port 2l and the upper end of the bypass port is closed by a plug Eile. In thisl event, the hum is eliminated from the return line as well as from the intake. In either event, a closed air pocket or chamber having a iiexible Wall sub- `iecteci to the fuel serves to eliminate the hum.

The forms of the invention illustrated in Figs. i to 3 may readily be used in circuits having return lines by removing the plusr 21' from the lower end o the bypass port 2l and inserting a plug 21a in the upper end thereof.

Aa illustrated herein, the exible wall is formed by means of a diaphragm made of an impregnated linen cloth which is water-proof and oilproof. It will be apparent that other exible or yieldable materials may be utilized for forming the diaphragm provided they are resistant to the oil with which they come in contact.

I claim as my invention:

l. A fuel pumpinar device having. in combination, a casing having a recess provided with an inlet port, and means forming a portion oi a return bypass port, pumping mechanism posi tioned in said recess, an outlet port in said casing through which the pumping; mechanism charges some of the pumped uei into the iiyp...;; port, a cover for said recess secured to said cas-4 ing, means positioned in said recess forming u closed air chamber having one iieixible wall sub Jected to the uel in said recess and another flex ible wall sealed from the fuel in said recess, and means for establishing communication between Said second flexible wall said return bypass port.

2. In coinbiiietion, i'uel pumping device having a casio provided with inlet. outlet, and retumhy-p l 'Le pressure operated valvemeana controlling said outlet and by-pass ports, pumping' mechanism in said casing adapted to draw fuel through the inlet port and force it out the outlet and. return ports, and means forming a closed air chamber having ilexible walls sub jected mdcpez-.identiy the fuel passing through the inlet port and the fuel passing through the return port.

G'UNNAR A. WAHLMAEK. 

